The present invention relates generally to lasers, and more specifically to ultrafast, high energy, and wavelength tunable pulsed light sources, particularly with fiber-based lasers.
Solid-state lasers combined with optical parametric oscillators (OPOs) based on χ(2) crystals are the current state-of-the-art for generating short pulsed laser radiation. They are most often used to generate a single, wavelength-tunable pulse train, but they are instrumental for the generation of synchronous trains of pulses operating at separated wavelengths. These synchronous pulse trains are useful in pump-probe measurements such as probing the carrier lifetimes in semiconductors, spectroscopically resolving fast chemical or biological reactions, and in any setting where multi-photon excitation is used.
The simplest synchronous systems have two stages, for example one can use two synchronized Ti:Sapphire oscillators or a wavelength tunable OPO that is pumped by a single Ti:Sapphire oscillator. Greater flexibility is achieved through greater complexity. One can use a multi-stage amplified Ti:Sapphire system and an optical parametric amplifier. The realization that ultrafast pulsed lasers can provide unique capability is resulting in a growing need for wavelength tunable pulsed sources of light at wavelengths where many biological materials have increased transparency. This window ranges in wavelength from about 900 nm up to 1500 nm, and it is not easily covered by Ti:Sapphire-based systems unless more than two stages are used, which increases manufacturing and operating time and cost.
Although commercial bulk optical systems are becoming more compact and user friendly, they are still quite expensive and there has been a trend towards using ultrafast fiber lasers. Bulk systems are currently superior to fiber lasers with the principal drawbacks of fiber lasers being limited wavelength tunability (e.g. a narrow range of available output wavelengths) and pulse duration flexibility (e.g. narrow range of pulse widths).
Therefore, it is desirable to provide inexpensive lasers with high power, wavelength tunability, and pulse duration flexibility.